Skin not allowing me to store in vault
Destroying an item unlocks the skin. Salvaging unlocks a skin, as well. I understand that particular item may not be salvageable, but you can destroy it.
If, for some odd reason, destroying doesn’t unlock it, perhaps you can obtain the skin on your Medium Armor-wearing character.
The items also say double-click to consume. Have you tried that?
If it’s a skin you cannot store, you need to actually use it before you unlock the skin.